Question

I am using Visual studio 2008.
For below code

double main()
{
}

I get error:

error C3874: return type of ‘main’
should be ‘int’ instead of ‘double’

But if i use below code

char main()
{
}

No errors.
After running and exiting the output window displays

The program ‘[5856] test2.exe: Native’
has exited with code -858993664
(0xcccccc00).

Question: Is compiler doing implicit cast from default return value of zero(integer) to char ?

how the code 0xcccccc00 got generated ?

Looks like last byte in that code seem to be the actual returned value. Why 0xcccccc is coming ?

Answer 1

The answer to your first question is sort of yes. A char is essentially a very small integral type, so the compiler is being (extremely) lenient. Double isn’t acceptable because it’s not an integral type. The 0xCCCCCC is memory that never got initialized (except for the purposes of debugging). Since ASCII characters can only have two hex digits, the conversion failed to set the first 24 bits at all (and just set the last 8 bits to 0). What an odd and undesirable compiler trick.